The Blue Fiend is one of the deadliest Robeasts from Planet Doom, it lived in seclusion until Witch Haggar summoned it to destroy Voltron. Along with Haggar this Robeast was responsible for Sven no longer being part of Voltron Force.

An Evil Voltron created from stolen blueprints by King Zarkon, and given the ability to read the electric impulses of the original by Haggar, thus allowing it to anticipate Voltrons next move before it is made.

Sent by King Zarkon to infiltrate the Voltron Force. Prince Bokar gained Allura's trust (and attraction) and was given the blue lion to pilot as his own, his true identity was discovered though and he reverted to his true form, a serpent like Robeast.

A group of savage warriors from Planet Doom. They hold a particular role of infamy in Voltron for being part of the shows goriest episode, where they were seen murdering large numbers of people, children included.

Claiming to be a slave who had been horrifically disfigured by Witch Haggar to the extent that his face was too gruesome for any human to look at, the masked man was in fact an agent of Planet Doom who took Princess Romelle hostage on Lotor's behalf planing to trade her for Allura. He was later revealed to be a stingray like robeast.

Captain of King Zarkon's forces, Yurak was one of the original villains of Voltron. Due to his many failures Yurak was eventually sentenced to death by King Zarkon, but instead of being executed Yurak voluntarily was transformed into a robeast to regain his honor.